PURPOSE: This study explores what dimensions of a health-related quality of life (HRQOL) questionnaire predict global ratings of overall quality of life (QOL) in lung cancer patients in assessments by patients and significant others, respectively. MATERIAL AND METHODS: The analyses were based on dyadic assessments from lung cancer patients and their significant others. A subset of scales and items from the Swedish version of the European Organization for Research and Treatment of Cancer (EORTC) QLQ C30 and the lung-cancer-specific module, LC-13, was selected. Using multiple regression procedures, the relative importance of different symptoms and of functional impairments in predicting overall QOL was examined. RESULTS: The multiple regressions revealed that emotional functioning and fatigue were the only significant predictors of overall QOL for both the patients and the significant others' assessments. In addition, physical functioning was found to be another predictor in the significant others' assessments. CONCLUSION: The results emphasize that it is essential to consider both emotional functioning and fatigue as important areas for overall QOL in lung cancer patients.